swscale/internal: constify and expose ff_swscale()

Used as an intermediate entry point for the new swscale context. The extra
constification is a consistency measure, as I want to move the memcpy of
stride and plane pointers to the functions that actually need to mutate them.

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Niklas Haas <git@haasn.dev>

libswscale/slice.c

@@ -145,7 +145,8 @@ int ff_rotate_slice(SwsSlice *s, int lum, int chr)
     return 0;
 }
 
-int ff_init_slice_from_src(SwsSlice * s, uint8_t *src[4], int stride[4], int srcW, int lumY, int lumH, int chrY, int chrH, int relative)
+int ff_init_slice_from_src(SwsSlice * s, uint8_t *const src[4], const int stride[4],
+                           int srcW, int lumY, int lumH, int chrY, int chrH, int relative)
 {
     int i = 0;
 

libswscale/swscale.c

@@ -233,10 +233,9 @@ static void lumRangeFromJpeg16_c(int16_t *_dst, int width)
     if (DEBUG_SWSCALE_BUFFERS)                  \
         av_log(c, AV_LOG_DEBUG, __VA_ARGS__)
 
-static int swscale(SwsContext *c, const uint8_t *src[],
+int ff_swscale(SwsContext *c, const uint8_t *const src[], const int srcStride[],
-                   int srcStride[], int srcSliceY, int srcSliceH,
+               int srcSliceY, int srcSliceH, uint8_t *const dst[],
-                   uint8_t *dst[], int dstStride[],
+               const int dstStride[], int dstSliceY, int dstSliceH)
-                   int dstSliceY, int dstSliceH)
 {
     const int scale_dst = dstSliceY > 0 || dstSliceH < c->dstH;
 
@@ -287,20 +286,29 @@ static int swscale(SwsContext *c, const uint8_t *src[],
     int hasLumHoles = 1;
     int hasChrHoles = 1;
 
+    const uint8_t *src2[4];
+    int srcStride2[4];
+
     if (isPacked(c->srcFormat)) {
-        src[1] =
+        src2[0] =
-        src[2] =
+        src2[1] =
-        src[3] = src[0];
+        src2[2] =
-        srcStride[1] =
+        src2[3] = src[0];
-        srcStride[2] =
+        srcStride2[0] =
-        srcStride[3] = srcStride[0];
+        srcStride2[1] =
+        srcStride2[2] =
+        srcStride2[3] = srcStride[0];
+    } else {
+        memcpy(src2, src, sizeof(src2));
+        memcpy(srcStride2, srcStride, sizeof(srcStride2));
     }
-    srcStride[1] *= 1 << c->vChrDrop;
+
-    srcStride[2] *= 1 << c->vChrDrop;
+    srcStride2[1] *= 1 << c->vChrDrop;
+    srcStride2[2] *= 1 << c->vChrDrop;
 
     DEBUG_BUFFERS("swscale() %p[%d] %p[%d] %p[%d] %p[%d] -> %p[%d] %p[%d] %p[%d] %p[%d]\n",
-                  src[0], srcStride[0], src[1], srcStride[1],
+                  src2[0], srcStride2[0], src2[1], srcStride2[1],
-                  src[2], srcStride[2], src[3], srcStride[3],
+                  src2[2], srcStride2[2], src2[3], srcStride2[3],
                   dst[0], dstStride[0], dst[1], dstStride[1],
                   dst[2], dstStride[2], dst[3], dstStride[3]);
     DEBUG_BUFFERS("srcSliceY: %d srcSliceH: %d dstY: %d dstH: %d\n",
@@ -320,10 +328,10 @@ static int swscale(SwsContext *c, const uint8_t *src[],
     }
 
 #if ARCH_X86
-    if (   (uintptr_t)dst[0]&15 || (uintptr_t)dst[1]&15 || (uintptr_t)dst[2]&15
+    if (   (uintptr_t) dst[0]&15 || (uintptr_t) dst[1]&15 || (uintptr_t) dst[2]&15
-        || (uintptr_t)src[0]&15 || (uintptr_t)src[1]&15 || (uintptr_t)src[2]&15
+        || (uintptr_t)src2[0]&15 || (uintptr_t)src2[1]&15 || (uintptr_t)src2[2]&15
-        || dstStride[0]&15 || dstStride[1]&15 || dstStride[2]&15 || dstStride[3]&15
+        ||  dstStride[0]&15 ||  dstStride[1]&15 ||  dstStride[2]&15 ||  dstStride[3]&15
-        || srcStride[0]&15 || srcStride[1]&15 || srcStride[2]&15 || srcStride[3]&15
+        || srcStride2[0]&15 || srcStride2[1]&15 || srcStride2[2]&15 || srcStride2[3]&15
     ) {
         SwsContext *const ctx = c->parent ? c->parent : c;
         int cpu_flags = av_get_cpu_flags();
@@ -356,7 +364,7 @@ static int swscale(SwsContext *c, const uint8_t *src[],
     ff_init_vscale_pfn(c, yuv2plane1, yuv2planeX, yuv2nv12cX,
                    yuv2packed1, yuv2packed2, yuv2packedX, yuv2anyX, c->use_mmx_vfilter);
 
-    ff_init_slice_from_src(src_slice, (uint8_t**)src, srcStride, c->srcW,
+    ff_init_slice_from_src(src_slice, (uint8_t**)src2, srcStride2, c->srcW,
             srcSliceY, srcSliceH, chrSrcSliceY, chrSrcSliceH, 1);
 
     ff_init_slice_from_src(vout_slice, (uint8_t**)dst, dstStride, c->dstW,
@@ -1054,8 +1062,8 @@ static int scale_internal(SwsContext *c,
         if (scale_dst)
             dst2[0] += dstSliceY * dstStride2[0];
     } else {
-        ret = swscale(c, src2, srcStride2, srcSliceY_internal, srcSliceH,
+        ret = ff_swscale(c, src2, srcStride2, srcSliceY_internal, srcSliceH,
-                      dst2, dstStride2, dstSliceY, dstSliceH);
+                         dst2, dstStride2, dstSliceY, dstSliceH);
     }
 
     if (c->dstXYZ && !(c->srcXYZ && c->srcW==c->dstW && c->srcH==c->dstH)) {

libswscale/swscale_internal.h

@@ -1121,7 +1121,8 @@ typedef struct SwsFilterDescriptor
 
 // warp input lines in the form (src + width*i + j) to slice format (line[i][j])
 // relative=true means first line src[x][0] otherwise first line is src[x][lum/crh Y]
-int ff_init_slice_from_src(SwsSlice * s, uint8_t *src[4], int stride[4], int srcW, int lumY, int lumH, int chrY, int chrH, int relative);
+int ff_init_slice_from_src(SwsSlice * s, uint8_t *const src[4], const int stride[4],
+                           int srcW, int lumY, int lumH, int chrY, int chrH, int relative);
 
 // Initialize scaler filter descriptor chain
 int ff_init_filters(SwsContext *c);
@@ -1165,6 +1166,11 @@ void ff_init_vscale_pfn(SwsContext *c, yuv2planar1_fn yuv2plane1, yuv2planarX_fn
 void ff_sws_slice_worker(void *priv, int jobnr, int threadnr,
                          int nb_jobs, int nb_threads);
 
+int ff_swscale(SwsContext *c, const uint8_t *const src[], const int srcStride[],
+               int srcSliceY, int srcSliceH, uint8_t *const dst[],
+               const int dstStride[], int dstSliceY, int dstSliceH);
+
+
 //number of extra lines to process
 #define MAX_LINES_AHEAD 4